The auxiliary draft device for a fireplace comprising the present invention is directed at improving the efficiency of consumption of fuel in the fireplace and also to reduce or prevent the removal of warm air in the room in which a fireplace is located which, under normal circumstances with conventional fireplaces, is required to provide some, if not most of the air required to cause the fuel of the fireplace to burn.
A fireplace of conventional design requires an inflow of air which, in turn, when heated, is lost up the chimney. Further, such air exhaust from a room causes a negative pressure inside the room and any adjoining rooms, thus causing cold air to flow in at any possible opening in the building in which the room is located. Obviously, such ingress of cold air causes unnecessary fuel consumption, particularly since it acts adversely to the conventional home heating system and requires a greater amount of heat from said system to counteract the cold air drawn in by such circumstances.
In modern homes which are highly effectively insulated, as well as in efficiently heated homes, a conventional fireplace is becoming prohibitively wasteful in terms of fuel consumption due to wasted warm air being consumed from the room by the fuel in the fireplace and resulting in drafts across floor areas. As a result of this, particularly in view of the present high cost of fuel, the use, if not the installation, of fireplaces is being reduced, although there is the possibility of greater use of the same in areas of abundant wood being available and the cost thereof being appropriately less than that of fuel oil and the like.
In such normal or conventional fireplaces, the air flow for igniting the fuel is through the front opening of the fireplace, then through the combustion chamber and up through the rear area of the combustion chamber, past the damper and into the smoke chamber and then up the flue. For greatest efficiency, such path of air flow is critical and any system that disrupts the even flow of such air results in inefficient burning of fuel and, under certain circumstances, causes the discharge of smoke into the surrounding room areas.
As described hereinafter, the present invention involves the use of an air curtain supplied across the front face of the fireplace opening. The principle of air curtains which effect separation of two chambers or spaces used at the entrance of stores, refrigerator rooms, and the like to prevent air flow between such spaces is well-known and proven. Providing such an air flow up across the front of a fireplace opening similarly tends to effectively separate and prevent any appreciable amount of the warm room air from the fireplace chamber while providing air to achieve combustion of the fuel in the fireplace and thereby effectively reduce air consumption from the surrounding room area.
The invention also includes the provision of an opening through a room wall adjacent the fireplace in order to permit the introduction of outside air to the fireplace. In this regard, it also is known that any opening through an outside wall of a building can be a source of unwanted cold air leaking into the building unless such an opening is closed at the outside wall.
Further, it also is quite well established that combustion within a fireplace chamber that is closed, for example, by glass doors across the face of the chamber frequently causes smoking of the glass with soot and tar due to the rolling of the smoke against the glass when the air flow is restricted. Further, it also is known that the burning of a fireplace of conventional configuration with glass doors across the front thereof, when closed, may cause overheating of the glass front, especially if the air intake vents which usually are provided in the lower portion of glass door assemblies and units are not open. But, when they are open, there obviously is a continual consumption of interior warm air by the fireplace obtained from the room and other vicinities near the fireplace from which such air is obtained.
It also is known to provide combustion air for fireplaces from sources outside of the room, such as exterior air, and also provide means for regulating the flow of such air to the fireplace. By way of example, prior U.S. Pat. No. 4,106,475, to Mayes, dated Aug. 15, 1978, and U.S. Pat. No. 4,137,895 to Bittinger, dated Feb. 6, 1979, respectively show the introduction of outside air directly to the lower part of the combustion chamber, and directed radially and inward toward the lower part of said combustion chamber. However, systems that direct auxiliary air, such as outside air, either at the back of the combustion chamber or immediately beneath the same, cause an intense blowing effect at the base of the fire which not only frequently causes more rapid consumption of fuel than otherwise, but also effects a disruption of the natural flame and fire patterns which are pleasing in appearance and thus, detract from the desirability and pleasure of a normal fireplace fire. These difficulties are obviated by the present invention, details of which are as follows: